Integrative and Comparative Biology Advance Access originally published online on February 15, 2008
Integrative and Comparative Biology 2008 48(3):439-441; doi:10.1093/icb/icn004
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Book Review |
An Introduction to Nervous Systems. Ralph J. Greenspan, editor.
Department of Zoology
NC State University, Raleigh, NC 27695
Correspondence: E-mail: Robert_Grossfeld{at}ncsu.edu
An Introduction to Nervous Systems. Ralph J. Greenspan, editor.
Woodbury, NY: Cold Spring Harbor Laboratory Press, 2007. 172 pp. ISBN 978-0-87969-0 (hardcover) $65.00, ISBN 978-0-87969-821-8 (paper) $45.00.
Over the past 30 years, there have been several iterations of books aimed at capturing in brief the essence of the organization and function of the nervous system. Not uncommonly, they extract general principles that would be more fully explored in a comprehensive text but do not otherwise deviate significantly from the traditional form and content of presentation. This one does. Ralph Greenspan is an established neuroscientist who has pioneered novel research to explore basic and cognitive aspects of nervous system function using the fruit fly as a model system. As he states in the Preface of this book, the Neurocience Institute, of which he is a staff scientist, aims to be a provocative academy, to "push the envelope." That philosophy is clearly conveyed in the creative, nontraditional style of presentation in this special book.
The title of the book, "An Introduction to Nervous Systems," is a bit misleading. A more accurate title, although cumbersome, would be something like "An Introduction to Nervous Systems through Examination of Some Invertebrate Models." The book uses select examples from invertebrate nervous systems to convey some fundamental principles that apply in some respects to the organization and function of the nervous system in general. In the final, short chapter—"Are All Brains Alike? Are All Brains Different?"—the author writes "Perhaps all nervous systems make use of common general strategies. Anatomical disparities may mask underlying functional similarities in the tasks performed by various circuits."
At first glance, it is surprising that nowhere in the text are there descriptions of what has been learned about ion channels and membrane potentials from classical studies of squid giant axons; of neural network properties from studies of the crustacean stomatogastric ganglion; of nervous system development from experiments on fruit fly nerve cord or nematode worms; of sensory signaling and reception from the moth or cricket; or of insect social structure, for example. The author's enthusiasm for Drosophila, which represents his main research subject, is reflected in a substantial fraction of the book. Moreover, there is little or no discussion of how the principles described are employed in mammals. Surveying the breadth of the neurobiology landscape seems not to be the primary purpose of this book. Rather, it describes select examples that highlight what studies of "simple" invertebrate nervous systems have taught us. The tales link organization of the nervous system to the organism's behavior, for which invertebrates have proven to be especially valuable. In a modern, molecular, mammalian research universe, the rich history of fundamental contributions of invertebrates to neuroscience may too often be overlooked. It is especially in this respect that the book is a welcome contribution to the neurobiological literature. In the introduction to Chapter 4—"Modulation, The Spice of Neural Life"—the author writes: "The capabilities of invertebrates have traditionally been underestimated. Perhaps this is because they are not warm and fuzzy ... For whatever reason, it has taken us an inordinately long time to realize that even the simplest animals have the capacity for modifying their behavior by adjusting the activities of their nervous systems. Perhaps this is a fundamental, inseparable property of nervous systems." Despite the fact that the book deviates from a traditional style, in its own way it follows a rather traditional sequence, e.g., membrane potentials, then chemical signaling and sensing, then neural circuits, then neuromodulation, then biological clocks, then higher, or cognitive, function.
There is a lot to like in this book, not only in its fascinating content but in the style of presentation. Ralph Greenspan weaves a tapestry about the molecular, cellular and network origins of function and behavior, and the implications for speciation, using a variety of invertebrate models. The images he creates are expressed as interesting, often humorous, readable stories about what some nervous systems do, how they do it, and how that has evolved using some basic principles in novel ways. Each chapter begins with a relevant quote or poem from a literary or scientific giant that sets the stage and tone for the often poetic introduction and description that follows. The stories themselves—about swimming in Paramecium and jellyfish, light detection by barnacles, decision making by marine snails, circadian rhythms, flying, and mating—are fascinating because they are set in a context of understanding the generation and modulation of behavior and, in some cases, the impact on ecology and evolution.
Although the author states in the Preface that the book is intended for the neurobiology novice possessing a basic introductory knowledge of biology, this reviewer believes that it would be more appropriate for an individual with an introductory neurobiological background. For example, in the very first chapter, one quickly discovers that understanding "simple" systems can be quite complex. In particular, students new to neurobiology often struggle with concepts underlying the generation of membrane potentials and the relationship of voltage and current, yet the text and figures require some understanding of these topics. In this respect, the Glossary at the end of the book seems uneven, defining some very basic biological terms yet not defining "receptor potential," for example, which is named but not explained in the caption of Figure 3.10.
Not to quibble, but this reviewer and two other neuroscientists who scanned the book question some statements or generalizations proposed, particularly in the Introduction ("What are Brains For"?). For example, on page 1 it states "When it comes to brains, size unquestionably matters." While that is no doubt true, it may be the organization of cells, i.e. the way they interact, that is more relevant. If it is size that is so important, then one should note that about three quarters of cells in mammalian brain are glial cells, not neurons, some potentially capable of modulating chemical signaling at up to 100, 000 synapses, yet their contributions are not mentioned (see below). Furthermore, spinal cords also possess much of the organization and cellular interactions, e.g., integrating sensory input and generating motor output, yet we view their capabilities as somewhat lacking in comparison with brain. What might be the fundamental differences between invertebrate and vertebrate nervous systems and between brain and spinal cord that yield unique aspects of functional competence? Or, are they as different as we imagine them to be, particularly in comparing function in invertebrates versus vertebrates? These are some interesting questions—not found in a typical comprehensive text—that might be explored a bit further in the Introduction and perhaps elsewhere in the book. In addition, on page 2, the author writes "Chemical sensing is almost certainly the original sense ...," yet mechanically gated ion channels that could sense changes in flow or pressure in the ambient environment are universal and also have been identified in prokaryotic organisms. Also, on page 4, the author writes "And because none of us wants to submit to being experimented upon ... we study animals." Yet, there is a substantial and rapidly growing literature that provides insights on the organization and function of human brain from studies of living persons—for example from functional MRI or stimulation/recording of brain of awake epileptic patients—or of postmortem tissue samples.
There are several other aspects of the book in its current form that would benefit from revision in a second edition. First, the emphasis is on how invertebrate nervous systems inform on nervous systems in general, but it is not clear in many cases to what extent the general organization of the behaviors is similar in invertebrates and vertebrates or whether similar molecules or mechanisms are used for different purposes. Does evolution mix and match bits and pieces of behavioral components that moves behavior in new directions? One also wonders whether there are good examples of invertebrate nervous systems and behaviors that do not translate well to a mammalian equivalent. Second, the book has a traditional neurocentric focus—and some invertebrates indeed have few glial cells—yet in the past couple of decades it has become abundantly clear from studies of mammalian systems that interactions of neurons with glia play vital roles in regulation of neural function, development and blood flow. Third, some of the figures could benefit from greater clarity or correction of the illustration or of the explanation in the caption, including citing the source link that is listed in the Bibliography at the end of the book. In addition, the Preface could note the location of the relevant Bibliography, currently organized by chapters but separate from them. It should be noted that the author also recently co-edited a much more comprehensive (800 pages), related book ("Invertebrate Neurobiology") with Geoffrey North.
In summary, this is an excellent book for gaining an appreciation for the links between form-function and behavior in the nervous system from invertebrate model systems and one that is interesting and enjoyable to read. It should be particularly valuable in inspiring budding or established life scientists to read more on the subject or even to become engaged in the pursuit of elucidating fundamental principles of neurobiology and behavior. It should stimulate broad questions about nervous systems and behavior. From a pedagogical perspective, I could imagine it being assigned as a short text in a general course on neurobiology and behavior or in a specialized neurobiology course that focuses on invertebrates or as a supplement to a more comprehensive text.
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